Multi-layer microscale or mesoscale structures are fabricated with adhered layers (e.g. layers that are bonded together upon deposition of successive layers to previous layers) and are then subjected to a heat treatment operation that enhances the interlayer adhesion significantly. The heat treatment operation is believed to result in diffusion of material across the layer boundaries and associated enhancement in adhesion (i.e. diffusion bonding). Interlayer adhesion and maybe intra-layer cohesion may be enhanced by heat treating in the presence of a reducing atmosphere that may help remove weaker oxides from surfaces or even from internal portions of layers.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A fabrication process for forming a plurality of multi-layer three-dimensional structures, comprising: (a) providing a substrate; (b) forming and adhering a first multi-material layer to a substrate, wherein the first multi-material layer comprises a desired pattern of at least one structural metal and at least one sacrificial metal; (c) forming and adhering a subsequent multi-material layer to a previously formed layer, wherein the forming and adhering of the subsequent multi-material layer comprises: a. selectively depositing at least one first metal using an adhered photoresist mask and thereafter removing the mask; b. depositing at least one second metal after removal of the mask; and c. planarizing the at least one first metal and the at least one second metal of the subsequent multi-material layer to set a boundary level for the subsequent multi-material layer, wherein the at least one first metal and the at least one second metal comprise at least one structural material and at least one sacrificial material; (d) repeating the forming and adhering operations of (b) and (c) at least once to build up a plurality of three-dimensional structures from a plurality of adhered multi-material layers; (e) after the forming of the plurality of adhered layers, releasing the plurality of three-dimensional structures from the at least one sacrificial material; (f) after formation of the plurality of adhered layers, subjecting the multi-layer structure to a heat treatment, wherein a maximum effective temperature during heat treatment is less than a recrystallization temperature of a selected one of the at least one structural material and is in a range of 150° C.-350° C., and wherein the heat treatment is applied for a sufficient time, at a sufficient temperature, and in an environment that results in average interlayer adhesion strength of the selected one of the at least one structural material exceeding one half of the average intra-layer yield strength of the selected one structural material after heat treatment.
2. The process of claim 1 wherein an average interlayer adhesion strength after the heat treatment is increased by at least a factor of two over the average interlayer adhesion strength prior to heat treatment.
3. The process of claim 1 wherein an average interlayer adhesion strength after the heat treatment is increased by at least a factor of five over the average interlayer adhesion strength prior to heat treatment.
4. The process of claim 1 wherein an average interlayer adhesion strength of the selected one of the at least one structural material after heat treatment is no less than the average intra-layer yield strength of the selected one of the at least one structural material after heat treatment.
5. The process of claim 1 wherein an average intra-layer adhesion strength of the selected one of the at least one structural material after heat treatment is at least as large as 75% of the average intra-layer yield strength of the selected one of the at least one structural material prior to heat treatment.
6. The process of claim 1 wherein an average interlayer adhesion strength of the selected one of the at least one structural material after heat treatment is no less than 50% of the ultimate tensile strength of the intra-layer material.
7. The process of claim 1 wherein any reduction in average intra-layer yield strength after heat treatment compared to before heat treatment is no more than 50% of an average intra-layer yield strength prior to heat treatment.
8. The process of claim 1 wherein the maximum effective temperature during heat treatment is in the range of 200° C.-350° C.
9. The process of claim 1 wherein an average intra-layer yield strength after heat treatment is no less than 75% of an average intra-layer yield strength prior to heat treatment.
10. The process of claim 1 wherein the at least one structural material comprises a material selected from the group consisting of nickel, nickel cobalt, and nickel.
11. The process of claim 1 wherein the maximum effective temperature during heat treatment is in the range of 250° C.-350° C.
12. A fabrication process for forming a plurality of multi-layer three-dimensional structure, comprising: (a) providing a substrate; (b) forming and adhering a first multi-material layer to a substrate, wherein the first multi-material layer comprises a desired pattern of at least one structural metal and at least one sacrificial metal; (c) forming and adhering a subsequent multi-material layer to a previously formed layer, wherein the forming and adhering of the subsequent multi-material layer comprises a. selectively depositing at least one first metal using an adhered photoresist mask and thereafter removing the mask; b. depositing at least one second metal after removal of the mask; and c. planarizing the at least one first metal and the at least one second metal of the subsequent multi-material layer to set a boundary level for the subsequent multi-material layer, wherein the at least one first metal and the at least one second metal comprise at least one structural material and at least one sacrificial material; (d) repeating the forming and adhering operations of (b) and (c) at least once to build up a plurality of three-dimensional structures from a plurality of adhered multi-material layers; (e) after the forming of the plurality of adhered layers, releasing the plurality of three-dimensional structures from the at least one sacrificial material; (f) after formation of at least a plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein a maximum effective temperature during heat treatment is less than a recrystallization temperature of a selected one of the at least one structural material and is in the range of 150° C.-350° C. and wherein the heat treatment is applied for a sufficient time, at a sufficient temperature, and in an environment that results in the formation of a structure which behaves monolithically up to at least the yield strength of the intra-layer material after heat treatment.
13. The process of claim 12 wherein the structures exhibit monolithic behavior up to the yield strength of the selected one of the at least one structural material after heat treatment.
14. The process of claim 12 wherein mechanical failure of the selected one of the at least one structural material is no more likely to occur due to interlayer adhesion failure than to intra-layer cohesion failure up through the elastic deformation range of the structures at heat treatment.
15. The process of claim 14 wherein a yield strength of the interlayer portions of the selected one of the at least one structural material after heat treatment is no less than 50% of the yield strength of the interlayer portions of the selected one of the at least one structural material before heat treatment.
16. The process of claim 15 wherein the no less than 50% is no less than 75%.
17. The process of claim 16 wherein a yield strength of the inter-layer portion of the selected one of the at least one structural material after heat treatment is greater than the yield strength of the inter-layer portions of the selected one of the at least one structural material prior to heat treatment.
18. The process of claim 16 wherein the selected one of the at least one structural material comprises a material selected from the group consisting of nickel, nickel cobalt, and nickel phosphor.
19. A fabrication process for forming a plurality of multi-layer three-dimensional structures, comprising: (a) providing a substrate; (b) forming and adhering a first multi-material layer to a substrate, wherein the first multi-material layer comprises a desired pattern of at least one structural metal and at least one sacrificial metal; (c) forming and adhering a subsequent multi-material layer to a previously formed layer, wherein the forming and adhering of the subsequent multi-material layer comprises: a. selectively depositing at least one first metal using an adhered photoresist mask and thereafter removing the mask; b. depositing at least one second metal after removal of the mask; and c. planarizing the at least one first metal and the at least one second metal of the subsequent multi-material layer to set a boundary level for the subsequent multi-material layer, wherein the at least one first metal and the at least one second metal comprise at least one structural material and at least one sacrificial material; (d) repeating the forming and adhering operations of (b) and (c) at least once to build up a plurality of three-dimensional structures from a plurality of adhered multi-material layers; (e) after the forming of the plurality of adhered layers, releasing the plurality of three-dimensional structures from the at least one sacrificial material; (f) after formation of the plurality of layers, subjecting the multi-layer structure to a heat treatment wherein a maximum effective temperature during heat treatment is less than a recrystallization temperature of a selected one of the at least one structural material and is in the range of 150° C.-350° C. and wherein the heat treatment is applied for a sufficient time, at a sufficient temperature, and in an environment that results in improved inter-layer adhesion after heat treatment such that the plurality of three-dimensional structures are no more likely to experience interlayer adhesion failure than intra-layer cohesion failure through an elastic deformation range of the structures (i.e. up to the beginning of the plastic deformation range of the structures) when under tension.
20. The process of claim 19 wherein the range is between 200° C.-350° C.
21. The process of claim 19 wherein the selected one of the at least one structural material is selected from the group consisting of nickel, nickel cobalt, and nickel phosphor.
22. A fabrication process for forming a plurality of multi-layer three-dimensional structures, comprising: (a) providing a substrate; (b) forming and adhering a first multi-material layer to a substrate, wherein the first multi-material layer comprises a desired pattern of at least one structural metal and at least one sacrificial metal; (c) forming and adhering a subsequent multi-material layer to a previously formed layer, wherein the forming and adhering of the subsequent multi-material layer comprises: a. selectively depositing at least one first metal using an adhered photoresist mask and thereafter removing the mask; b. depositing at least one second metal after removal of the mask; and c. planarizing the at least one first metal and the at least one second metal of the subsequent multi-material layer to set a boundary level for the subsequent multi-material layer, wherein the at least one first metal and the at least one second metal comprise at least one structural material and at least one sacrificial material; (d) repeating the forming and adhering operations of (b) and (c) at least once to build up a plurality of three-dimensional structures from a plurality of adhered multi-material layers; (e) after the forming of the plurality of adhered layers, releasing the plurality of three-dimensional structures from the at least one sacrificial material; (f) after formation of the plurality of layers, subjecting the multi-layer structure to a heat treatment, wherein a maximum effective temperature during heat treatment is less than a recrystallization temperature of a selected one of the at least one structural material and is in the range of 150° C.-350° C., wherein a post heat treatment intra-layer yield strength of the selected one of the at least one structural material is no less than 50% of a pre-heat treatment intra-layer yield strength of the selected one of the at least one structural material, and wherein the heat treatment is applied for a sufficient time, at a sufficient temperature, and in an environment that results in improved inter-layer adhesion after heat treatment such that the plurality of three-dimensional structures experience a reduced percentage of failures in inter-layer adhesion through an elastic deformation range of the structures (i.e. up to the beginning of the plastic deformation range of the structures) than would be present in absence of the heat treatment.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 20, 2014
February 14, 2017
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